Susanne Pagoldh says in her book Nordic Knitting that you need 1300 yds of wool for this.
You cast on the outer edge in the example I am giving. Since I am using a fingering weight yarn and a size 5 (I think) needle, I will CO 580 sts. A heavier yarn ( and correspondingly bigger needle) would probably be about 350-450 sts. I haven't done one like that, so I'm not sure. Mark the center stitch with a marker or a thread.
You don't want a shawl like this to roll, so plan on knitting in garter for most of it, with some openwork and/or ribbing thrown in for good measure and interest. Plus the garter st is reversible, and they were made this way traditionally so you good wear them on either side and therefore wash them less often...
The stitches are relatively open on this shawl, hence the larger needle for smaller yarn.
The rule on this shawl is to K2 together at the beginning and end of each row, and K2 together after the center stitch marker each row. (dec 3 sts each row) This ensures that your shawl gets smaller. It ends up as a kind of boomerang shape, very long.
I knit each row (garter st) for about 16 rows, and then do this:
keep doing your standard decreases, and *K2 together, YO* for one whole row.
Do 3 rows in the garter stitch pattern, and then do one row in the *K2 together, YO* (that's a basic eyelet, folks) pattern.
You could follow that with with 8 rows of ribbing, or just more garter st, and then do another set of eyelets, as above.
After that, I do a longer stretch of garter, maybe 12-16 rows, and then the eyelet set again. And repeat until it's done.
Once you are done knitting, you can crochet around the whole outside, or not. You can add fringe on the bottom edge, or not. The pattern i first learned this from called for both of the above, and I did neither, and they all turn out beautiful!
The knitting goes on and on endlessly, especially if you are used to knitting up quick items, but believe me, it will get smaller (fewer sts to work each row) and when you are done, you will have something you can't buy anywhere!
Very simple! and open for interpretation.
You may even get hooked on these and have to make one a year. Or more. (I'm working on my third...)
This shawl is both functional and elegant, and is sure to get you tons of compliments...!
It's also a good way to get started knitting finer gauge stuff.